Consistent unwrapping
What you want is Project from View (Bounds). That will take what you see in the view and put it over top of the image, stretching it to fit.

Note that since the image you're mapping it to is square, this will likely make it too tall for your figure; you'll then have to scale your UV map down in the UV/Image Editor to make the squares actually be square. (Of course, you can just crop your image in an external program like GIMP to  have the right number of squares.)